Lovoa trichilioides (PROTA)
|Geographic coverage Africa|
|Geographic coverage World|
|Carbohydrate / starch|
Lovoa trichilioides Harms
- Protologue: Bot. Jahrb. Syst. 23: 165 (1896).
- Family: Meliaceae
- Chromosome number: 2n = 50
- Lovoa brownii Sprague (1906),
- Lovoa klaineana Pierre ex Sprague (1906).
- African walnut, tigerwood, Congowood, brown mahogany (En).
- Noyer d’Afrique, noyer du Gabon (Fr).
Origin and geographic distribution
Lovoa trichilioides is widespread, from Sierra Leone east to western Uganda, and south to north-western Tanzania and northern Angola.
The wood (trade name: dibetou) is highly valued for furniture, cabinet work, flooring, carpentry, joinery, interior trim, stairways, panelling and decorative veneer and plywood. It is locally used for house construction, vehicle bodies, implements and handles, and to make canoes. It is suitable for ship building, sporting goods, toys, novelties, railway sleepers, carving, boxes, crates, turnery and pulpwood. It is also used as firewood and for charcoal production.
In Congo pulped bark is rubbed on the chest to treat pulmonary troubles. The bark is also used against dental caries. The tree is occasionally planted as a roadside tree. It is promoted in Uganda for tree planting programmes; it is locally planted as a shade tree in agroforestry programmes, for crops such as coffee and banana. The flowers are a source of nectar for honey bees.
Production and international trade
Around 1970 Côte d’Ivoire was the most important exporter of dibetou logs with annual export volumes of about 80,000 m³ between 1968 and 1974. Cameroon exported 13,100 m³ and 10,400 m³ of sawn wood in 2003 and 2004, respectively, and 9900 m³ in 2006. In Gabon the export of dibetou logs was 10,400 m³ in 1991, decreasing to an annual average of 5100 m³ in 2000–2004. The sawn wood export from Gabon was 1000 m³ in 2001, at an average price of US$ 239/m³. Congo exported 2100 m³ of logs in 2004, and 4100 m³ in 2006. Ghana exported small amounts of African walnut plywood: in 2003, 2004 and 2005, at an average price of US$ 398/m³, US$ 352/m³ and US$ 383/m³, respectively.
The heartwood is yellowish brown to greyish brown, often with golden and blackish markings, and distinctly demarcated from the pale brown to pale grey, 3–7 cm wide sapwood. The grain is usually interlocked, texture moderately fine to fine. The wood is lustrous and has an attractive appearance, with a ribbon-like aspect on quarter-sawn surfaces. It has a cedar-like scent.
The wood is medium-weight, with a density of 450–610(–680) kg/m³ at 12% moisture content. With some caution, it air dries and kiln dries well, with only slight risk of distortion and checking. The rates of shrinkage are medium, from green to oven dry 2.8–5.3% radial and 5.6–8.8% tangential. Once dry, the wood is stable in service.
At 12% moisture content, the modulus of rupture is 70–119 N/mm², modulus of elasticity 7300–11,600(–14,900) N/mm², compression parallel to grain 39–59 N/mm², shear 6–10 N/mm², cleavage 10–18 N/mm, Janka side hardness 4180–4220 N and Janka end hardness 5000–5030 N.
The wood is easy to saw and work; ordinary equipment can be used. There is some tendency of picking up of grain when the wood is quarter-sawn, and planing may be difficult because of the presence of interlocked grain, resulting in tearing. A cutting angle of 15–20° is recommended. Tools should be kept sharp. The nailing and screwing properties are good, although there may be some tendency to splitting. The wood finishes well, but for a fine polish the use of a filler is recommended. The gluing, painting and varnishing properties are satisfactory, the steam bending properties moderate.
The wood is rather susceptible to fungal, termite and dry-wood borer attacks, and very susceptible to attack by marine borers. In a test in Ghana in which the wood was exposed to the termite Coptotermes formosanus, active feeding of the termite on the wood was noted. The heartwood is resistant to impregnation by preservatives. The sawdust may be irritant.
In the seed oil, dienoic unsaturated acids predominate.
- Evergreen large tree up to 45 m tall; bole branchless for up to 25(–30) m, usually straight and cylindrical, sometimes sinuous, up to 120(–200) cm in diameter, slightly thickened at base or with short buttresses; bark surface greyish brown to blackish brown, smooth to scaly, with many lenticels, inner bark pinkish red with whitish streaks, fibrous, with strong sweet smell; crown dense, dark green; twigs glabrous.
- Leaves alternate, paripinnately or imparipinnately compound with (5–)10–15 leaflets, glabrous; stipules absent; petiole 3–9 cm long, channelled and slightly winged, rachis 4–20(–30) cm long; petiolules 2–10 mm long; leaflets opposite to alternate, elliptical to oblong-lanceolate, 5–25 cm × 2–10 cm, cuneate to rounded at base, obtuse to acuminate at apex, leathery, pinnately veined with closely spaced lateral veins.
- Inflorescence an axillary or terminal panicle up to 40 cm long, glabrous.
- Flowers functionally unisexual, regular, 4-merous; pedicel 1.5–3 mm long, jointed; calyx lobed almost to the base, 1–2 mm long; petals free, elliptical, 4–6.5 mm long, white, tinged greenish or reddish; male flowers with stamens fused into a cup-shaped tube with 8 anthers at margin, ovary not functional; female flowers with superior, globose ovary, 4-celled, gradually passing into the style, stigma head-shaped, stamens not functional.
- Fruit a pendulous, tetragonal capsule 4–7 cm × 1–1.5 cm, black, dehiscing with 4 valves, many-seeded with seeds attached to the top of the central column.
- Seeds 4–6 cm long including the large apical wing.
- Seedling with epigeal germination, but cotyledons often remaining within the testa; hypocotyl 3–4 cm long, epicotyl 2–3 cm long; first 2 leaves opposite, with 2 pairs of leaflets.
Other botanical information
Lovoa comprises 2 species, both confined to tropical Africa. It belongs to the tribe Swietenieae and is related to Entandrophragma, Khaya and Pseudocedrela.
Lovoa swynnertonii Baker f. occurs in eastern DR Congo, Kenya, Uganda, Tanzania, Zimbabwe and Mozambique, in rainforest up to 1500 m altitude. It differs from Lovoa trichilioides by its asymmetrical leaflets and hairy inflorescences, but is otherwise similar. Its wood has been used for similar purposes as that of Lovoa trichilioides. Lovoa swynnertonii has been subject to heavy exploitation in many regions and is rare almost everywhere in its distribution area; it is listed as endangered in the IUCN Red list.
Wood-anatomical description (IAWA hardwood codes):
- Growth rings: 2: growth ring boundaries indistinct or absent.
- Vessels: 5: wood diffuse-porous; 13: simple perforation plates; 22: intervessel pits alternate; 23?: shape of alternate pits polygonal; 24: intervessel pits minute (≤ 4 μm); (25: intervessel pits small (4–7 μm)); 30: vessel-ray pits with distinct borders; similar to intervessel pits in size and shape throughout the ray cell; 42: mean tangential diameter of vessel lumina 100–200 μm; 47: 5–20 vessels per square millimetre; 58: gums and other deposits in heartwood vessels.
- Tracheids and fibres: 61: fibres with simple to minutely bordered pits; (65: septate fibres present); 66: non-septate fibres present; 69: fibres thin- to thick-walled.
- Axial parenchyma: (76: axial parenchyma diffuse); 78: axial parenchyma scanty paratracheal; 79: axial parenchyma vasicentric; (80: axial parenchyma aliform); (81: axial parenchyma lozenge-aliform); 83: axial parenchyma confluent; (84: axial parenchyma unilateral paratracheal); 92: four (3–4) cells per parenchyma strand; 93: eight (5–8) cells per parenchyma strand.
- Rays: 98: larger rays commonly 4- to 10-seriate; 104: all ray cells procumbent; 106: body ray cells procumbent with one row of upright and/or square marginal cells; 114: ≤ 4 rays per mm; 115: 4–12 rays per mm.
- Secretory elements and cambial variants: 131: intercellular canals of traumatic origin.
- Mineral inclusions: 136: prismatic crystals present; 142: prismatic crystals in chambered axial parenchyma cells.
Growth and development
Natural regeneration is often abundant, although the seed suffers heavy predation. Seedlings of about 20 cm tall may be abundant even in full shade, where they may survive for several years, but saplings only grow where gaps develop in the forest canopy. Early growth is generally slow, with planted seedlings reaching 100 cm height in 2 years and 150 cm in 3 years. In exceptional cases trees reach a height of 2.5 m after 1 year. After the first years, growth becomes faster, and there are records of young trees attaining 9 m in height after 7 years. In plantations in Uganda an average bole diameter of 25 cm was reached after 25 years, whereas in Nigeria and Cameroon a mean annual diameter increment of 1.0–1.8 cm was recorded. In experiments in Gabon, 11-year-old trees planted in light shadow were 20 m tall and 16.5 cm in diameter, whereas growth of trees planted in full sun was slower. In natural forest the mean annual diameter increment is about 5 mm.
In West Africa trees flower in the dry season and fruits are ripe in February–April. However, seeds are not produced each year; in Liberia and Nigeria good seed years reportedly occur every 3–4 years. The seeds are dispersed by wind, turning like a propeller while falling. The presence of vesicular-arbuscular mycorrhizal fungi of the genus Glomus in the soil close to Lovoa trichilioides trees has been demonstrated.
Lovoa trichilioides occurs scattered in evergreen forest and semi-deciduous forest, up to 1200 m altitude. It prefers moist but free draining localities on alluvial soils and more than 2000 mm annual rainfall. In Ghana it is strongly associated with acid soils. In Uganda it is common in mixed rainforest along Lake Victoria, but can also be found in gallery forest and thickets.
Propagation and planting
For planting, seeds are collected from the forest floor, although many seeds may already be attacked by insects. The 1000-seed weight is 100–230 g. The seed including the wing is usually covered for up to three-quarters with soil. Seeds have a short viability, with up to 90% germination for fresh seed, but only about 30% germination after 2 months. Seeds start germinating after 8–16 days. They should be stored in sealed containers and ash should be added because they are very susceptible to insect attack. Wildlings are sometimes used for planting; they should be watered abundantly. A successful method of propagation by stem cuttings has been developed in Cameroon. Long, thin cuttings with large leaf areas (50–200 cm²) made from apical nodes of multi-stemmed stock-plants rooted best, with a rooting rate of up to 60%. Stem cuttings rooted best in coarse gravel. The application of auxins had no clear effect on rooting.
For transplanting in the forest, seedlings in bags should be about 50 cm tall. Stumps or striplings 150–180 cm long can also be used. For planting in the field it is recommended to plant under moderate shade and to avoid full sun. It has been reported that trees developed very successfully when planted in groups or lines in thinned natural forest. In an experiment in Gabon, 100% of planted seedlings survived 1 year after planting, both in sites that had been clear-cut and in sites where the forest canopy was opened up and the undergrowth removed. After 6 years, survival was 94% in the undergrowth of opened-up forest, with trees having a mean height of 11.6 m and a mean bole diameter of 11.2 cm, and only 76% in clear-cut sites, with trees having a mean height of 8.9 m and a mean bole diameter of 7.0 cm. Initial weeding is important and climbers have to be removed. It is difficult, however, to progressively remove the shade without hurting the saplings.
In the forest, large trees of Lovoa trichilioides generally occur scattered. In southern Cameroon densities of trees with a bole diameter larger than 60 cm vary between 3 boles and 25 boles per 100 ha, and the average bole volume varies between 0.15 m³ and 2.3 m³ per ha. In Côte d’Ivoire, the Central African Republic, Gabon and Congo the densities are generally low, with less than 1 bole of more than 60 cm diameter per 10 ha, but in south-eastern Gabon up to 1 bole per 2 ha may occur. In Liberia the average number of exploitable trees is 12 per 100 ha, locally up to 25.
In Cameroon approximately 6400 ha have been planted with Lovoa trichilioides. Plantations have also been established in Côte d’Ivoire, Nigeria and Uganda. Pruning prevents early branching and is advantageous for timber production. In Nigeria it is recommended that pure stands of Lovoa trichilioides be thinned to about 300 trees per ha by the 15th year, and to 100 trees per ha by the 30th year, to enable the trees to attain a diameter of about 90 cm in 60–70 years.
Diseases and pests
Large-scale destruction of seedlings by shoot borers has been recorded. In Cameroon longhorn beetles, borers, scale insects and defoliator insects are the main pests observed in young plantations, and collar decay also occurs. Antelopes and rodents eat the bark of seedlings and young trees. Fruits and seeds are subject to heavy predation by insects such as Catopyla dysorphnaea.
In natural forest the minimum diameter for felling is 60 cm in Côte d’Ivoire and DR Congo, 70 cm in Liberia, Ghana and Gabon, and 80 cm in Cameroon and Central African Republic. Some caution is needed during felling operations because logs may have heart shakes and brittle heart.
Trees with a bole diameter of 60, 100, 140 and 180 cm yield about 3.0, 10.9, 22.7 and 38.4 m³ of timber, respectively. In Cameroon the annual average yield has been recorded as only 1.8 m³/ha, but this was attributed to planting in unfavourable localities.
Handling after harvest
When logs are left in the forest for some time, treatment with preservatives is recommended. Logs float in water and can be transported by river.
Lovoa trichilioides is included in the IUCN Red list of threatened species as vulnerable, mainly because exploitation rates are high.
Lovoa trichilioides wood is in high demand on the international market, which resulted in much pressure on natural populations. It has become vulnerable, and the establishment of methods of sustainable forest management for this species are needed. It can be expected that rotation cycles of about 50 years are needed for sustainable harvest. Lovoa trichilioides is recommended for forest enrichment planting.
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Correct citation of this article
Nyunaï, N., 2008. Lovoa trichilioides Harms. In: Louppe, D., Oteng-Amoako, A.A. & Brink, M. (Editors). PROTA (Plant Resources of Tropical Africa / Ressources végétales de l’Afrique tropicale), Wageningen, Netherlands. Accessed 22 March 2023.
- See the Prota4U database.